17 replies to this topic

[james4563]

Something has happened to my VXT (Stage4 Courtney), it's got a lumpy idle hot & cold, sort of surges between 500-800rpm on idle. It's in a pattern, like idles okay for maybe 5-10 seconds and then dips and rises then okay again for 5-10 seconds. Repeat.

It's like this video someone has posted on youtube, but it drops a bit lower before recovering: https://www.youtube....h?v=IB7IlT6KCF8, there's no solution on the video unfortunately though.

 

I've basically tried most of the suggestions I've found on the forum, the cheapest options anyway.

 

http://i142.photobuc...VacuumPipe1.jpg

I have checked the vacuum hoses can't find any leaks, I pulled off the hose on the above image labeled 'Vacuum box RHS' and covered the nipple (   ) didn't seem to change anything. Covered the end of the pipe too. The bit that goes to the bottom of the throttle body is really stuck on, I can't pull it off and I have zip tied around the FPR and T joints I can get at. The only bit I haven't been able to fully check is the BCS because it's very hard to get at from above.... ( any tips )?

 

 

I have also tried 2 sets of plugs:

• BKR6EK ( Platinum and 1 grade cooler than stock I believe )
• BKR7EIX ( Iridium and 2 grades cooler I think )

Both sets were brand new before they went in, I thought the 7's might have been causing it because they were too cool, however it's the same with the 6's. It does feel like overall it runs smoother with the BKR6EK.

I gapped the 7's to 0.7mm but the 6's can't be gapped I don't think as the design is a bit different. They are like this: https://c1552172.ssl...121713_x800.jpg

 

 

The car has only done 28K.

I saw on here about disconnecting the AMM, which I did and the car nearly stalled, but then recovered and idled a bit higher; still seemed to have it's lumpy seeking revs. I guess that means the AMM is okay?

 

 

Would the next step be coil pack? Can the coil pack cause bad idle even though the car seems to run fine under boost? I did remove the coil pack and clean it all up, including the springs and where they connect inside the rubbers. It didn't seem that bad really, minimal corrosion.

 

Sorry for a long post.... 

Edited by james4563, 14 October 2016 - 09:22 PM.

[Nev]

[font="'arial unicode ms';"]Check the following (in order of likelihood/simplicity/cheapness):[/font]

• [font="'arial unicode ms';"]A boost leak from your post turbo pipe-work, ideally perform a pressure test to 2 Bar.[/font]
• [font="'arial unicode ms';"]Possible MAF failure (a common problem), swap it out with a known working one.[/font]
• [font="'arial unicode ms';"]Possible coil-pack failure, swap it out with a known working one.[/font]
• [font="'arial unicode ms';"]Possible cracked intercooler (the vertical welds seams sometimes fail).[/font]
• [font="'arial unicode ms';"]Faulty throttle body (very rare) or TB to inlet manifold gasket seal.[/font]
• [font="'arial unicode ms';"]Faulty loom affecting the MAF (extremely rare).[/font]

[font="'arial unicode ms';"]I'd say from your preliminary checks that the first point is the most likely, so perform the following test:[/font]

 

 

[font="'arial unicode ms';"]Boost Pipe Pressure Test[/font]

[font="'arial unicode ms';"]This test will identify if you have any leaks from the boost pipe system (from the turbo into the cylinder head). The way to test for this is to:[/font]

• [font="'arial unicode ms';"]Disconnect the 2" black rubber boost pipe (described above) from the turbo compressor outlet.[/font]
• [font="'arial unicode ms';"]Insert a homemade 2” I/D bung into the end of the black rubber boost pipe, with standard 1/4 inch air compressor nipple. This can be made from odds and sods from B&Q (plastic pipe + wood + eBay 1/4" air nipple).[/font]
• [font="'arial unicode ms';"]Using an air compressor, pressurise the system up to approx 2 Bar.[/font]
• [font="'arial unicode ms';"]Listen for any leaks which will be very audible. NB: If all valves of the engine are not closed, turn the crank over until they shut, otherwise air can be heard passing the throttle-body into the cylinders and out of the valves.[/font]

 

Whilst you have this problem try to avoid boosting hard with the turbo or you may over-speed it and damage the impeller blades.

 

Edited by Nev, 15 October 2016 - 07:06 AM.

[james4563]

The for sale listing says my car has [color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;]80mm AFM, will that just be a AFM from the astra VXR ( is it the only option )?[/color]

 

I'm thinking in case I need to replace it. Standard AFM will obviously be no good because of the remap, so I need to make sure I get the right one.

[Nev]

The for sale listing says my car has [color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;]80mm AFM, will that just be a AFM from the astra VXR ( is it the only option )?[/color]

 

I'm thinking in case I need to replace it. Standard AFM will obviously be no good because of the remap, so I need to make sure I get the right one.

 

Correct, it's the so called 80mm MAF off the Astra VXR (which is actually only 72mm I/D).

 

If you decide to buy one, please make sure you get a genuine Bosch part from a reputable source, as the copy parts are terrible and there are many so called Bosch eBay items that are simply copies too.

Edited by Nev, 17 October 2016 - 02:22 PM.

[AstonVauxhall]

The for sale listing says my car has [color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;]80mm AFM, will that just be a AFM from the astra VXR ( is it the only option )?[/color]

 

I'm thinking in case I need to replace it. Standard AFM will obviously be no good because of the remap, so I need to make sure I get the right one.

 

Part numbers for Z20LEH AFM are;

 

93186084 which has been superseded to 93181894

 

Price seems to have risen quite a bit since I last checked - £233+VAT from Vauxhall.

[Johnboyhgt]

Andrew pages ? 

or Eurocar parts ? 

[james4563]

Eurocar parts have the astra VXR AFM.

 

http://www.eurocarpa...6d094966

 

If you put in the code WEEKEND30 you get 30% discount at the moment too.

 

Brings it too: £109.19

 

 

 

[james4563]

Do bosch make the OE coilpacks, or Hella?

On the eurocarparts website they've got a cheap coil pack and then Bosch/Hella one, I picked bosch/hella and when I went to collect I said to the guy I was excepting it to be Bosch as I thought they made the packs for vauxhall. He told me that Hella must make them not Bosch, and they are OE spec.

 

I was pretty sure Bosch made the coil pack? Am I better going with one from autovaux? 

 

The Hella one they gave me does look the same as the one currently fitted to my car. However I don't know for sure if that's even OE.

[AstonVauxhall]

Vauxhall/Opel have a variety of suppliers and they do just change. 

 

I looked up a coilpack for a Corsa D this morning, original part number X made my AC Delco, now superseded to part number X made by Delphi. 

 

I would guess original would be Bosch. 

 

Part number - 9198834. AutoVaux list GM and Bosch. 

[pezley]

Had exactly the same, Jez at BOT found it was the cambelt assembly had been put on in reverse (before I owned it)

 

Anaologue Autos nor Absolute Autos (down sooooooouth) couldnt find the issue and Jez found it with in minutes of looking. Top chap

 

This was after checking MAF, Coil Pack (love replacing spark plugs for no reason) & air leaks

Edited by pezley, 18 October 2016 - 12:49 PM.

[james4563]

Had exactly the same, Jez at BOT found it was the cambelt assembly had been put on in reverse (before I owned it)

 

Anaologue Autos nor Absolute Autos (down sooooooouth) couldnt find the issue and Jez found it with in minutes of looking. Top chap

 

This was after checking MAF, Coil Pack (love replacing spark plugs for no reason) & air leaks

 

Anyone know how I could check this?

I don't expect it would be the issue as BoT and Courtney did all the work on the car, so I'd think it would have been put on right.

Worth checking though, thanks pezley.

 

I did test another coil pack today, wasn't the issue as it idled the same with the changed coilpack

[siztenboots]

its possible that if the cambelt top cover, was installed wrong, ( or I have seen one with all the bolts missing ) , then the camshaft sensor could be pushed out of position as it only has one small locating bolt. if that camshaft sensor not working, then the ecu would switch to wasted spark and wasted injection, plus you would notice it was not happy revving over 4500. it would still get you home, but the obvious way to test would be unplug , then slide out camcover, and carefully pinch plug and disconnect. with it unplugged it might start a bit less quickly as it cannot detect which 4 stoke phase the camshaft position is, but should start even if the cams have jumped a tooth or two.

[james4563]

its possible that if the cambelt top cover, was installed wrong, ( or I have seen one with all the bolts missing ) , then the camshaft sensor could be pushed out of position as it only has one small locating bolt. if that camshaft sensor not working, then the ecu would switch to wasted spark and wasted injection, plus you would notice it was not happy revving over 4500. it would still get you home, but the obvious way to test would be unplug , then slide out camcover, and carefully pinch plug and disconnect. with it unplugged it might start a bit less quickly as it cannot detect which 4 stoke phase the camshaft position is, but should start even if the cams have jumped a tooth or two.

 

I presume if this was the case though the car would run like trash? It seems to pull good all the way to redline. Are you talking about removing the whole camcover ( grey ) or just the black cover that goes over the spark plugs?

 

Maybe I'm being picky, but the idle seems off to me. Normal idle should result in the rev needle not moving right? It shouldn't dip down and back up at all if running well. 

I'm getting a lot of flutter too, maybe I need to recheck for vac leak. When the revs drop the exhaust burbles too, you can hear it's not quite idling right from that exhaust sound.

[siztenboots]

if you have flutter then vacuum is not operating the recirc valve properly , which is likely to be a leak and your idle problem as well. the cover referred to above, is the "Turbo" logo black cover, which the camsensor cable passes through.

[james4563]

if you have flutter then vacuum is not operating the recirc valve properly , which is likely to be a leak and your idle problem as well. the cover referred to above, is the "Turbo" logo black cover, which the camsensor cable passes through.

 

Okay thanks, I'll double check the vac lines and report back.

Is it just the lines in this picture to check or are there more vac lines?

http://i142.photobuc...VacuumPipe1.jpg

 

Are there more round the other side nearer the turbo? Does the line that comes from the recirc valve go all the way around to the vacuum box mentioned in the above picture?

 

Is there any online link to how the turbo charger works on the Z20LET? In regards to the vacuum lines and boost solenoids etc?

[james4563]

Checked the vacuum with a boost gauge and it's showing -20hg, I believe this is normal.

Does that rule out a vacuum leak? I teed the boost gauge into the line that goes onto the FPR.

 

Want to run a compression test, can someone tell me which fuse I need to pull in order to not flood the engine with fuel.

[tibby]

Do you have an idle like this? https://youtu.be/PHyWW63DXKg Solution over here was: Irridium spark plugs

[Nev]

Checked the vacuum with a boost gauge and it's showing -20hg, I believe this is normal.

Does that rule out a vacuum leak? I teed the boost gauge into the line that goes onto the FPR.

 

Want to run a compression test, can someone tell me which fuse I need to pull in order to not flood the engine with fuel.

 

-20 Hg vac isn't particularily strong (but nothing to worry about either). Some cars manage -25 Hg vac.

 

After double checking your vac lines, check the diaphram in the turbo isn't knackered.

 

If that does't fix it then the next thing to check is leaks from the inlet manifold area + TB + top hat. You could try using soapy bubbles sprayed over the area and see if any get sucked up at the joints.

 

Did you ever do the boost pipe pressure test (as I can't remember)?

Edited by Nev, 23 October 2016 - 09:20 PM.